The audit of I-9 forms, known as a silent raid, was the reason the San Jose based company voluntarily joined the federal E-Verify system to check the immigration status of all new hires.

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Jose Machado, left, holds a sign in Spanish that reads "No Dreamer left Behind" during a news conference of students seeking temporary relief from deportation in Miami, Tuesday, Aug. 15, 2012. Hundreds of thousands of young illegal immigrants scrambled to get papers in order Wednesday as the U.S. started accepting applications to allow them to avoid deportation and get a work permit but not a path to citizenship. (AP Photo/Alan Diaz)

Federal immigration agents launched an audit of the 22 store Mi Pueblo supermarket chain in mid-August after hearing complaints about suspected illegal immigrants working at the stores, the company announced Friday.

The audit of I-9 forms, known as a silent raid, was the reason the San Jose based company voluntarily joined the federal E-Verify system to check the immigration status of all new hires, according to the Mercury News.

The announcement comes days before a threatened shopper boycott is to begin at noon Monday, led by a union trying to organize Mi Pueblo's more than 3,000 workers.

Labor organizers trying to unionize Latino and Asian ethnic markets across the state picked up the E-Verify revelation to attack chain owner Juvenal Chavez because he himself is said to have come to the United States illegally from Mexico as a young man in the 1980s, though he is now a U.S. citizen, according to the newspaper.

Founded in 1991 by Chavez, a former Stanford University janitor, the company now has stores from Vallejo to Salinas and in the Central Valley.